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ENDOCRINE SYSTEM—MICROSCOPIC and GROSS ANATOMY
I. Pituitary Gland: The
2 pituitary gland lobes derive from different embryologic tissues.
The gland is located in the brain area.
A. Anterior
Pituitary Lobe
1. Composed of glandular tissue
2. Appears darker staining compared to posterior lobe
3. Secretes many hormones (GFLAT P)
Growth Hormone
Follicle Stimulating Hormone (FSH)
Luteinizing Hormone (LH)
AdrenoCorticoTropic Hormone (ACTH)
Thyroid Stimulating Hormone (TSH)
Prolactin
B. Posterior
Pituitary Lobe
1. Composed largely of pituicytes and nerve fibers
2. Appears less cellular (smaller # of nuclei) and lighter staining than
anterior lobe
3. Stores and releases hormones that are made in the hypothalamus
Oxytocin
Anti-Diuretic Hormone (ADH)
C. Infundibulum
(need to know for model only): Stalk that attaches posterior pituitary
to brain
II. Thyroid Gland
A. Grossly composed
of 2 symmetric lateral lobes attached by an isthmus. Located over
the trachea just inferior to (below) the
larynx.
B. Microscopically
composed of many colloid filled follicles. The colloid is pink in
color and homogeneous in nature. Colloid is
composed of thyroglobulin and iodine and is the storage form of the thyroid
hormones T3 and T4,
which are secreted into the
blood stream. The follicles are lined with simple cuboidal or squamous
epithelium. The larger the follicle, the thinner the
epithelium is in appearance. In the connective tissue between the
follicles there are scattered parafollicular cells (or C-cells),
which are lighter staining than the follicle cells. The parafollicular
cells secrete calcitonin, which acts to lower
blood calcium
levels.
III. Adrenal Gland
A. Located on the
superior poles of both kidneys. Similar to the pituitary gland in
that it is composed of 2 different tissue types.
Surrounded by a relatively thick connective tissue capsule.
B. Adrenal
Cortex: Composed of glandular tissue. Secretes a number
of hormones collectively known as corticosteroids.
1. Zona glomerulosa: Lies just adjacent to the capsule.
Thinnest of the layers. This layer secretes mineralocorticoids e.g.
aldosterone.
2. Zona fasciculata: Next layer. Thickest of the cortical
layers. Is generally lighter staining than flanking layers. This
layer
secretes glucocorticoids e.g. cortisol.
3. Zona reticularis: Innermost cortical layer. Darkest
staining of the cortical layers. This layer secretes gonadocorticoids
e.g.
androgens (sex hormones).
C. Adrenal
Medulla: Innermost section of the gland and composed of nervous
tissue. Surrounds the central vein of the organ. This
region secretes epinephrine and norepinephrine.
IV. Pancreas
A. Located in the
mesentery of the duodenum (mesoduodenum). Has exocrine and endocrine
functions.
B. Islets
of Langerhans: Small specialized endocrine regions or “islets”
located within the exocrine portion of the pancreas.
Composed of 2 cell types (alpha and beta). Alpha cells secrete glucagon
which increases blood sugar and beta cells secrete insulin
which decreases blood sugar.
C. Acini
(or acinar) Cells: Glandular tissue that is dark staining
compared to the islet cells. The acinar cells secrete digestive
enzymes which travel through a duct system to reach the duodenum.
V. Fetal Pig Anatomy
A. Thyroid
Gland: A dark structure located on the ventral aspect of the
trachea just caudal to the Larynx. (NOTE the different
terminology in the pig – caudal instead of inferior and ventral instead
of anterior).
B. Cervical
Thymus Gland: A lobed gland located on each side of the neck
C. Thoracic
Thymus Gland: A lobed gland located over the base of the heart
VI. Other Organs (know for endocrine
model)
A. Parathyroid
gland: Associated with the thyroid gland. Secretes PTH
which
? Ca2+ levels.
B. Testes:
Located in the scrotum of males. Responsible for producing testosterone.
C. Epididymis:
Attached to the testes, tubular network for transporting and storing sperm.
D. Ovaries:
Located near the uterus in females. Responsible for producing estrogen
and progesterone.
E. Fallopian
tubes (Oviducts): Run from the ovary to the uterus.
Responsible for transport of ova.
**KNOW WHAT HORMONES ARE SECRETED BY WHICH GALNDS AND BE ABLE TO IDENTIFY WHAT CONDITIONS ARE ASSOCIATED WITH HYPER- AND HYPO-SECRETION OF EACH HORMONE.**
REPRODUCTIVE SYSTEM—MICROSCOPIC and GROSS ANATOMY
I. Testes: Have both exocrine
(sperm) and endocrine (testosterone) functions (see page 1081 in text).
A. Composed of a number
of coiled seminiferous tubules which generally appear in crosssection on
microscope slides. The “mortar”
of the tubules is the Sertoli cells, which form a tight junction preventing
the sperm from entering the body or anything from the
body interacting with the sperm. The Sertoli cells also act as nurse
cells and provide nutrients to the developing sperm.
1. Spermatogonia: Stem cells that line
the outer edges of the tubules.
2. Spermatocytes: the “middle” layer
of cells within the tubules. Generally will have larger, darker staining
nuclei than the
spermatids
3. Spermatids: Those cells nearest to
the lumen, further along in development than the spermatocytes. In
late spermatids,
appearance is similar to that of mature sperm.
B. Interstitial
or Leydig cells: located in the connective tissue surrounding
the seminiferous tubules. Produce androgens e.g.
testosterone.
II. Ovaries: Have both
exocrine (ova) and endocrine (estrogen and progesterone) functions (page
1087).
A. Primordial Follicle:
Generally found on outer surface of ovary in large clusters or “nests.”
Composed of an oocyte surrounded by
a single layer of thin squamous-like follicle cells.
B. Primary Follicle:
Composed of one or more layers of cuboidal or low columnar-type granulosa
cells surrounding an oocyte. The
oocyte is larger than seen in the primordial follicles.
C. Secondary Follicle:
Composed of multiple layers of granulosa cells surrounding an oocyte.
Fluid filled spaces are starting to
appear between layers of the granulose cells.
D. Graafian Follicle:
The fluid filled spaces hat began in the secondary follicle have coalesced
to form a complete antrum. The
oocyte is surrounding by a layer of granulosa cells. The entire follicle
is surrounded by multiple layers of cells.
III. Uterus: Composed
of three layers, perimetrium – visceral peritoneum; myometrium – thick
layer of smooth muscle; endometrium –
innermost layer composed
of simple columnar epithelium with an underlying lamina propria, a highly
cellular connective tissue layer
where the glands are
located.
A. Proliferative
Phase: Days 6-14 of a typical 28 day cycle. Occurs between
menstruation and ovulation. The uterus is preparing
a surface for implantation of the fertilized ovum. Numerous glands
present, but not as coiled as in the secretory phase.
B. Secretory
Phase: Days 15-28 of a typical 28 day cycle. Occurs
between ovulation and menstruation. The uterine glands
enlarge, coil and begin secreting nutritious glycoproteins into the uterine
cavity which will sustain the embryo until implantation
has occurred.
C. Menstrual
Phase: Days 1-5 of a normal 28 day cycle. The endometrium
is sloughed off if pregnancy is not signaled. Generally
fewer glands than in either of the other phases.
IV. Fetal Pig Anatomy
A. Right
and Left vas deferens: The vas deferens is a continuation
of the epididymis and carries the sperm from the scrotal region
to the urethra.
B. Right
and Left Epididymis: The epididymis looks like a crescent
moon surrounding the testicle.
C. Right
and Left testis: Very small in the fetal pig. Looks
like a miniature lima bean.
D. Right
and Left Ovary: Very small in the fetal pig. Located
at the end of the uterine horns.
E. Uterine
Horns: The uterus of the pig has 2 long slender horns that
extend from the body (Y shaped) DO NOT CONFUSE
THESE FOR THE OVIDUCTS (FALLOPIAN TUBES)
F. Uterus:
The body of the uterus extends from the cervix, which can be palpated as
a firm enlargement in the reproductive tract,
to the bifurcation of the uterine horns. Remember that the uterus
lies between the rectum and the bladder.
G. Vagina:
The vagina is located caudal (behind) the cervix and ends at the vulva
which can be seen externally just ventral to the
anus. The easiest way to identify the vagina is to palpate the cervix
and go caudal. If no cervix is palpable, it is where the
reproductive tract widens.
V. Human Reproductive Models
A. Male: See page
1071 in text for image that is similar to the model in the lab
B. Female: See
page 1086 in text for image that is similar to the model in the lab
The following web site has images of similar
reproductive models, however, I strongly encourage all students to look
at the models in OUR lab that will be on the exam.
http://bioweb.uwlax.edu/APlab/Table_of_Contents/Lab_17/lab_17.html
Also, remember to look at the web sites listed in the lab manual on page 85. The images on these sites may be on the exam. These images are also available on the lab computers as described in your lab manual.